Fabrication and tribological properties of superhydrophobic nickel films with positive and negative biomimetic microtextures

Abstract

Nickel (Ni) films with positive and negative textured surfaces of lotus and rice leaf patterns were fabricated through an inexpensive and effective method. The as-prepared Ni films were superhydrophobic and exhibited excellent tribological properties after chemical treatment. Experimental results indicated that the water contact angles (WCAs) on the surfaces of biomimetic textured Ni films (approximately 120°) were far greater than those on smooth films (65°). The biomimetic textured surfaces became superhydrophobic (WCA of approximately 150°) after perfluoropolyether (PFPE) treatment, which could be due to the combined effects of the special texture and the PFPE. The as-prepared biomimetic-textured Ni films modified with PFPE were improved with a low friction coefficient and excellent antiwear properties, which were due to the combination of the effective lubrication of PFPE and the special textures that served as a good lubricant and a debris reservoir. Moreover, the antiwear properties of the as-prepared Ni films with negative biomimetic microtextures modified with PFPE were much better than those of films with positive biomimetic microtextures modified with PFPE.

Multi-Scale Surface Texturing in Tribology—Current Knowledge and Future Perspectives

“…General classification and examples for each type of texturing method [41]. Having the generation of multi-scale surface textures in mind, they can be fabricated in a multi-step [44][45][46][47][48][49] or single-step [50][51][52] process. Naturally, single-step processes are less time-consuming, easier to integrate into production lines, and therefore more efficient.…”

“…If performed correctly, however, this approach can lead to pronounced multi-scale textures with a homogenous distribution of both texture types over the surface, as can be seen in Figure 3. Additionally, multi-scale textures can be manufactured by replicating natural surfaces inhibiting a multi-scale surface topography like the lotus leaf [44][45][46]75]. Shafiei and Alpas mimicked the natural surface texture of lotus leaf and boa's skin using a cellulose acetate film.…”

“…In a subsequent step, a nanocrystalline nickel layer is deposited onto this film to obtain the positive surface texture of the natural sample [45,46]. To add surface textures on another scale to the lotus leaf replicas, an additional Additionally, multi-scale textures can be manufactured by replicating natural surfaces inhibiting a multi-scale surface topography like the lotus leaf [44][45][46]75]. Shafiei and Alpas mimicked the natural surface texture of lotus leaf and boa's skin using a cellulose acetate film.…”

“…Additionally, they verified that the wear resistance was improved when using a final chemical PFPE treatment. The observed results were traced back to the good lubrication abilities of PFPE films as well as the possibility to reduce the real area of contact and to trap wear particles in the surface textures [44]. Using a combination of nanocasting, electroplating, and physical vapor deposition, Wang et al fabricated diamond-like carbon films with Lotus leaf-like textures thus aiming at generating hard and flexible coatings with superhydrophobicity and good tribological properties.…”

Drag reduction methods at solid-liquid interfaces

“…To obtain superhydrophobic surfaces, methods developed can be divided into three ways according to different principles. The first one is to construct microstructures on the low surface energy substrates [107], the second one is to modify the rough surfaces with low surface energy materials [108], and the third one is to spray coatings containing nanoparticles and low surface energy materials on the substrates [109,110]. It has been pointed out that surface microstructure is the main factor determining the superhydrophobic properties rather than low surface energy materials, as it's hard to achieve superhydrophobicity only by changing the surface free energy.…”